A tunnel broker with the Tunnel Setup Protocol (TSP) enables the establishment of tunnels of various inner protocols, such as IPv6 or IPv4, inside various outer protocols packets, such as IPv4, IPv6 or UDP over IPv4 for IPv4 NAT traversal. The control protocol (TSP) is used by the tunnel client to negotiate the tunnel with the broker. A mobile node implementing TSP can be connected to both IPv4 and IPv6 networks whether it is on IPv4 only, IPv4 behind a NAT or on IPv6 only. A tunnel broker may terminate the tunnels on remote tunnel servers or on itself. This document describes the TSP protocol within the model of the tunnel broker model.